(1) Field of the Invention
The invention relates to closed cell phenolic foam insulation having improved physical and mechanical properties. The physical and mechanical properties which are improved include friability, facer adhesion, cell wall strength, shrinkage, compressive properties and appearance. The invention also relates to improvements to the process of preparing the closed cell phenolic foam insulation. The pressure temperature profile and foam viscosity are improved.
(2) Prior Art
Commercially acceptable closed cell phenolic foam insulation has been known for about the past eight years. Phenolic foam has the best fire rating of any known polymeric foam insulation. Phenolic foam does not sustain a flame even when contacted by the flame of a blow torch and gives off minimal amounts of toxic gases. Phenolic foams can stand temperatures of 375.degree. F. without serious degradation. Phenolic foams have an ASTM-E-84 Steiner Tunnel Flame Spread Rating around 25, a fuel contribution of about 25 and a Smoke Developed Rating of about 25. In addition to having the best fire retardant properties available closed cell phenolic foam is the most efficient foam insulation available. Closed cell phenolic foam has an aged R value of 8.33 per inch. Additionally unlike many other high R foam insulations the thermal insulation properties of closed cell phenolic foam do not degrade over time.
Commercially acceptable phenolic foam having the properties described above and a composition for making the same are described in Doerge U.S. Pat. No. 4,423,163 and in Carlson et al. U.S. Pat. Nos. 4,444,912; 4,478,958 and 4,539,338. In accordance with these patents a commercially acceptable closed cell phenolic foam is prepared by foaming and curing a foamable resole composition comprising certain critical aqueous phenol formaldehyde resoles, chlorofluorocarbon blowing agent, surfactant and optional additives such as plasticizers and formaldehyde scavengers. The foaming and curing is accomplished with certain critical anhydrous aryl sulfonic acids in a substantially closed mold. The aqueous phenol formaldehyde resole is essentially a phenol formaldehyde condensation polymer having a molar ratio of formaldehyde to phenol of from about 1.7:1 to 2.3:1, preferable from 1.75:1 to 2.25:1 and most preferably about 2:1. The resole has a weight average molecular weight greater than 800 and preferably from 950-1500. The resole also has a number average molecular weight greater than about 350 and preferably from about 400 to 600 and a dispersivity greater than about 1.7 preferably from 1.8 to 2.6. The critical acid foaming and curing catalyst is an anhydrous aryl sulfonic acid having a pKa less than about 2.0 and which changes the compatibility of the phenolic resole with water sufficiently enough to prevent perforations and ruptures in the cell walls caused by water. The preferred anhydrous aryl sulfonic acid is a combination of toluene sulfonic acid and xylene sulfonic acid.
The general method for preparing closed cell phenolic foam using the compositions set forth above is well known. Generally, the foamable phenolic resole composition is prepared by admixing aqueous phenolic resole, blowing agent, surfactant, optional additives and acid curing catalyst into a substantially uniform mixture. The curing catalyst initiates the curing reaction which is highly exothermic. The exotherm of the curing reaction vaporizes and expands the blowing agent thereby foaming the compositions. The foaming is performed in a substantially closed mold.
The general method for the continuous manufacture of closed cell phenolic foam insulation board on a commercial scale is as follows. The foamable phenolic resole composition is prepared by continuously feeding into a suitable mixing device the aqueous phenolic resole, blowing agent, surfactant, optional additives and acid curing catalyst. The ratio of the various ingredients is varied depending on the desired density, thickness, etc. of the final product. The mixing device combines these ingredients into a substantially uniform composition which is continuously applied evenly onto a moving substrate which is usually a facer material for the foam such as glass fiber mat, cardboard or metal foil such as aluminum foil. The foaming composition is then covered with a facer material of usually the same type as the lower facer material. The foaming composition is then passed into a double belt press type apparatus where the curing exotherm continues to vaporize and expand the blowing agent, thereby foaming the composition as it is cured. During the foaming and curing the facer material is adhered to the foam.
Even though closed cell phenolic foam made with the compositions described above and in the general manner described above is the most efficient foam insulation and has the best fire properties, it can be improved. For example, the compressive strength or damage resistance of the closed cell phenolic foam is commercially acceptable. Damage resistance, however, is not as high as some competitive foam insulations. Similarly phenolic foam has commercially acceptable friability and punking properties, however, these properties are not as good as desired. The shrinkage of closed cell phenolic foam made in accordance with the prior art described above is also commercially acceptable but is not as low as desired. The adhesion of phenolic foam to the facer materials could also be improved even though the current adhesive strength does not present any significant problem. Similarly the strength of the cell walls of phenolic foam made as described above is very good, however it is always desirable to improve the strength of the cell walls. The strength and thickness of the cell walls are critical to the long term thermal performance of the phenolic foam. Weak cell walls will not withstand the thermal expansion and contraction that foam insulation undergoes. The appearance of the current closed cell phenolic foam is acceptable but it is always desirable to manufacture a better looking product. Finally, the general compositions and method described above can be readily practiced on a commercial scale, however, it is always desirable to make improvements to any commercial process.
Alkyl glucosides, particularly various methyl glucosides, are well known commercially available products. Methyl glucosides have been used in urethane foams as part of the polyol. Methyl glucosides can be used to manufacture polyester polyols and polyether polyols. When used as polyols for manufacturing urethane foam it is claimed in the literature that the methyl glucosides increase the dimensional stability of the urethane foam. Urethane and isocyanurate foam insulations have a tendency to grow and the methyl glucoside reduces the tendency of these foams to increase in size. It is also claimed that the methyl glucosides improve the flame properties of the urethane foam. The literature also claims that polyols made with methyl glucosides are compatible with the blowing agents, improve the viscosities of the foaming mixture and improve the reaction exotherm of the foaming urethane.
Methyl glucosides are also suggested for use in adhesives based on amino and phenol formaldehyde resoles. Methyl glucosides may be used as a comonomer or extender in adhesives made from phenol formaldehyde resoles or from urea phenol formaldehyde resoles. According to the product literature methyl glucoside as an extender or comonomer in adhesives based on urea phenol formaldehyde resoles or phenol formaldehyde resoles increases solution stability, improves resole clarity, improves flow properties, improves plasticization and reduces free formaldehyde. Additionally it is claimed that methyl glucosides improve the penetration of the adhesive into cellulosic materials, improve tack, improve glue performance and reduce glue consumption.
The product literature for methyl glucosides also claim that phenolic resin binders extended with methyl glucosides as a comonomer are useful as binders for thermal insulation. Phenolic resins binders containing 10-20 weight percent methyl glucosides are good binders for lose fill or heavy density fiberglass insulation and for intermediate or heavy density mineral wool. It is also mentioned that methyl glucoside are binders for phenolic foam insulation however phenolic foam insulation does not have binders.
Accordingly it is an object of the present invention to provide an improved closed cell phenolic foam and an improved method for making the same using alkyl glucosides, particularly methyl glucosides. In particular it is an object of this invention to improve the friability and damage resistance, reduce the shrinkage, increase the strength and thickness of the cell walls, and increase facer adhesion of closed cell phenolic foam by using small amounts of alkyl glucosides. The use of the glucosides also improve the process for making the closed cell phenolic foam by improving the pressure temperature profile and improving the foam viscosity.
Additional objects and advantages of the present invention will be apparent to those skilled in the art by reference to the following description and drawings.